Safety switch for de-energizing a driving motor in the event of stoppage of a shaft driven thereby



March 7, 1967 v. A. BARNHART 3,308,406

SAFETY SWITCH FOR DE'ENERGIZING A DRIVING MOTOR IN THE EVENT OF STOPPAGEOF A SHAFT DRIVEN THEREBY Filed June 5, 1964 m, mwm

United States Patent 3,308,406 SAFETY SWITCH FOR DE-ENERGIZING A DRIV-ING MOTOR IN THE EVENT OF STOPPAGE OF A SHAFT DRIVEN THEREBY Vilas A..Barnhart, Waupaca, Wis., assignor to A. E. Moore Company, Inc.,Waupaca, Wis., a corporation of Wisconsin Filed June 3, 1964, Ser. No.372,231 Claims. (Cl. 335-74) This invention relates to a safety switchfor de-energizing a driving motor in the event of stoppage of a shaftdriven thereby.

An example of apparatus in which the device is useful is the door openershown in my application Serial No. 316,740, filed October 16, 1963 andpertaining, specifically, to a lost motion accumulator in a reversibledrive.

In the door opening mechanism selected to exemplify the invention, thereis a screw shaft which may be rotated by power in either direction whenthe door is to be opened or closed. The impulse which initiates doormovement is momentary. Hence, a stepping switch functions like a holdingcircuit to maintain energization of the motor until the manual controlswitch is closed, or the door completes its movement, or the movement isobstructed. In any such case, the mechanism opens the holding circuitand movement terminates.

If there is a stoppage for any reason, severe damage may be done eitherto the mechanism or to the motor or perhaps to the body of a personsubjected to pressure by the movement of the door, unless the motor isdeenergized under these conditions.

Accordingly, I have provided a drive, associated switches and switchactuators so organized that regardless of the direction of rotation ofthe shaft the circuit will remain closed as long as the shaft is inrotation but will be opened to tie-energize the motor if rotation of theshaft is arrested, even momentarily.

A yoke through which the shaft passes carries at least one switch, ifonly one direction of movement is involved, or two switches if the shaftis reversible. These switches are connected in series. Both switches arenormally closed to actuate the stepping relay to a position in which themotor is de-energized. At least one will be held open during normalshaft rotation by the arm of a member frictionally engaged with theshaft. However, if the shaft rotation is obstructed, a clutch slips. Theswitches are mounted on a yoke which rides on the eccentric hub of thedriving pulley so that the normally open switch .will be closedmomentarily under these conditions by eccentric displacement of the yokeon which the switches are mounted. This will step the relay tode-energize the motor.

In the drawings:

FIG. 1 is a diagrammatic view partially in elevation and partially inaxial section through a shaft driving arrangement embodying theinvention.

' FIG. 2 is a greatly enlarged detail view taken in section on the line22 of FIG. 1.

FIG. 3 is a view similar to FIG. 2 showing the parts in a differentposition which they assume if the shaft stops rotating.

FIG. 4 is a view of the switch mounting and operating mechanism inperspective, with the frictionally driven part shown in a relativelyseparated position.

FIG. 5 is a circuit diagram.

While the invention is by no means limited to a door operator, I haveselected a door operator to exemplify the invention. The screw shaft isdriven from pulley 12 through a slip clutch which includes friction disk14. A belt 16 connects the pulley 12 with the armature shaft 3,308,406Patented Mar. 7, 1967 18 of an electric motor 20. A compression spring22 is seated against nut 24. The spring 22 exerts pressure on the clutchelement 26 which is keyed to the shaft 10 and bears against the frictiondisk 14. Thus the shaft normally receives torque from pulley 12.

An extension 28 projecting axially from the hub of pulley 12 is slightlyeccentric with respect to the axis of shaft 10. The yoke 30 has upperand lower arms 32 and 34 respectively embracing top and bottomperipheral portions of the eccentric hub extension 28. The degree ofpreferred eccentricity of hub extension 28 is indicated by the lines 36and 38 in FIG. 2, the line 36 being at the level of the axis of the hubextension 28 and the line 38 being at the level of the axis of shaft 10.

The yoke 30 is confined within a casing 40 which encloses switches 42and 44, respectively mounted on the yoke arms 32 and 34. The contacts 46and 48 of the normally closed switches are respectively mounted on arms50 and 52 in the path of the end portions of switch actuators 54 and 56,respectively. These actuators are guided for reciprocation in theterminal portions 58 and 60 of the yoke. Their respective inner ends 61are spaced to receive the arm 62 of a split ring 64 embracing the shaft10 and frictionally driven therefrom.

The motor 20 is reversible. As shown in FIG. 5, it receives the fullvoltage of the line 66. A transformer at 68 reduces line voltage forcontrol circuit purposes.

The control switch 70 may be operated manually or electrically or byradio. When closed, it energizes solenoid 72. The resulting movement ofits armature 74 causes one step of rotation of the ratchet 76 of thestepping relay. The shaft 78 advances the rotary relay contact 80 andthe rotary relay contact 82 in steps of 45. As clearly shown in FIG. 5,each of the rotors 80 and 82 has diametrical conductors 84 crossing atright angles. Their intervening position is indicated by the brokenlines 85. When lines 85 register with fixed contacts 86 and 88, there isno electrical connection between the fixed contacts. A one tooth advanceof the ratchet 76 will alternately close and open the circuits throughthe respective switch rotors 80- and 82. Thus the assembly may beconsidered, in one sense, to function like a holding relay because,after the circuit is once established, it remains established until thesolenoid 72 is next energized, whereupon the circuits are promptlybroken until further energization of the solenoid 72 occurs.

The switch rotor 80 controls the low voltage circuit while switch 82controls the energization of the operating motor 20 at line voltage.

As long as shaft 10 is in operation in either direction, frictionbetween it and the split ring 64 causes arm 62 to displace one or theother of the switch actuators 54 or 56 and thereby to open one or theother of the switches 42 or 44.

In case of any stoppage of shaft 10, the friction drive through disk 14will permit the motor 20 to continue to operate. The slight eccentricityof the hub extension 28 of pulley 12 assures that the entire yoke 30will have vibratory movement with respect to the shaft if the shaft isstationary while the hub extension 28 continues to revolve. If thiscondition were to persist for any appreciable length of time, thefriction clutch would be destroyed. However, if the shaft 10 stops whilethe hub extension 28 continues to be rotated by the motor 20, actingthrough bent 16 on pulley 12, the resulting vibratory movement of theyoke 30 will assure that the parts will assume the position shown inFIG. 3 in which the two switches 42 and 44 are both closed.

There will be a tendency for the parts to assume the position shown inFIG. 3 even without the eccentricity of the hub extension upon which theyoke is mounted. However, the vibration resulting from the eccentricmounting assures that the parts will function positively to deenergizethe motor immediately upon cessation of rotation of shaft 10.

When the two switches 42 and 44 are both closed as above described andshown in FIG. 3, a circuit will be established from ground 96 throughconductor 98 and switch contacts 88 and 86- to the solenoid 72 andthence back to the secondary of transformer 68. The resultingenergization of the solenoid 72 will advance the stepping relay one step(45) thus registering the non-conductive areas 85 of the respectiverotors 80 and 82 with their respective fixed contacts. This immediatelystops the motor 20 and de-energizes the low voltage control circuits.The closing of switch 70 will again advance the stepping relay ratchet76 to rotate the rotors 80' and 82 for another 45 thereby setting up thelow voltage circuits of the safety switch mechanism and at the same timeenergizing the motor 20. In the particular device, the reversing switchat '100 (which is conventional in such devices) will, in the instantstructure, cause shaft to operate in a reverse direction from that inwhich it last operated.

There is a limit switch which is not here involved but will be referredto briefly. The bar 102 moves along screw 6 and in its path are springcontacts 104 and 106 shown in FIG. 5. Engagement of the bar 102 acrossspring contacts 104 and 106 will have the same effect as the functioningof the safetyswitch as above described in that it will connect theground 108 through line 110 and line 98 to the fixed contact 88 of rotor80, current being conducted through the conductor 84 to the other fixedcontact 86 and thence through the solenoid 72 with return throughcondductor 112 to the secondary of transformer 68. The resultingenergization of solenoid 72 of the stepping relay will advance the relay45, thereby stopping motor and de-energizing the entire control circuit.

The starting of motor 20 and the energizing of the control circuit canalways be effected by the switch 70. The de-energization of the motor 20and the control circuit can be accomplished either through the safetyswitches 42 and 44 as above described or by further manipulation of theswitch 70 as above described or by the engagement of moving limit switchcontact 102 with spring contacts 104 and 106 as above described.

I claim:

1. The combination of a motor, a driven shaft, means for communicatingmotion from the motor to the driven shaft, a rotor having a slip clutchconnection with the shaft, a safety switch mechanism' includingrelatively movable parts one of which is connected with the rotor andanother of which is connected with said shaft, and means wherebyrelative movement between said parts deenergizes the motor in the eventof slippage of said clutch, said last means including:

a mounting having means supporting the mounting for oscillation,

complementary means respectively mounted on the shaft and the rotor foreffecting oscillation of the mounting upon the occurrence of movement inthe slip clutch connection between the shaft and the rotor,

a switch on the mounting including switch contacts,

a switch actuator constituting means for displacing one of said contactswith respect to the other, said actuator being provided with a frictionclutch driving connection with said shaft separate from the slip clutchconnection first mentioned,

a motor energizing and de-energizing switch,

means for electrically operating said last switch to deenergize saidmotor,

means for electrically connecting said last mentioned means in circuitwith the aforesaid contacts of the switch on said mounting,

the circuit through said contacts holding the motor energizing andde-energizing switch in motor energizing position by the friction clutchactuation of the switch actuator from the shaft during normal rotationof the shaft, the said mounting being stationary,

the motor energizing and de-energizing switch being operated to motorde-energizing position upon the occurrence of oscillation of themounting consequent upon relative movement between said rotor and saidshaft.

2. The combination of a motor, a driven shaft, a rotor having means fordriving it from the motor and having slip clutch connection with theshaft for normally operating the shaft from the motor, an eccentricconnected with the rotor, a yoke riding on the eccentric to receivemotion therefrom, a switch mounted on the yoke and having normallyclosed contacts, a motor controlling circuit in which said switch isconnected, an arm having friction drive connection with the shaft toreceive motion therefrom tending to rotate the arm with the shaft, meansfor opening one of the contacts of the switch with respect to the otherof said normally closed contacts and constituting an actuator comprisingmeans for receiving motion from said arm when such motion is impartedfrictionally to the arm from said shaft, whereby the switch tends to beheld open during shaft rotation, said eccentric and yoke constitutingmeans effective during continued operation of the eccentric for bringingabout the closing of the said switch contacts of said switch when shaftmotion is arrested.

3. The combination of a driven shaft and electrically controlledreversible means for the rotation thereof, said means including adriving rotor having slip clutch connection with the shaft and having aneccentric portion, switch means controlling the energization andde-energization of said electrically controlled means and includingswitch contact elements at opposite sides of the shaft and oppositelyextending actuators therefor, an arm having frictionally drivenconnection with the shaft and disposed between said actuators wherebysaid arm selectively operates one of said actuators from said shaftaccording to the direction of rotation of the shaft, relatively fixedcontacts with which the respective contact elements cooperate and fromwhich the said one element is displaced, and means for energizing andde-energizing said electrical means, said energizing and de-energizingmeans including a circuit controlled by the actuatoreffected movement ofsaid opposed switch elements, and a mechanism engaged by the eccentricportion of said rotor for effecting bodily movement of said contacts ina direction to engage one of said switch elements which has beendisplaced by its respective actuator at a time when the movement of theshaft is arrested.

4. A combination according to claim 3 in which the respective fixedcontacts and switch contact elements are mounted on a yoke having armsat opposite sides of the shaft and said yoke has bearing contact on aneccentric hub with which the driving rotor is provided and whichconstitutes the eccentric portion of said rotor aforesaid.

5. The combination of a screw shaft and a reversible motor, a steppingrelay including a rotary switch member having alternate contact elementsand insulated elements, contact means controlling the energization ofthe motor and respectively positioned at the periphery of the rotor toengage alternately during rotor rotation with the contact elements andinsulated elements of said rotor, electrical means-for the steppedadvance of said rotor, a driving member operatively connected to receivemotion from the motor and having a slip clutch connecting it with saidshaft, said member having an eccentric hub, a yoke having guide meansfor positioning the yoke, the yoke including arms engaged with theeccentric hub,

actuators 'engageable with the respective movable con- 5 tacts anddisposed generally oppositely to each other, and an arm interveningbetween said actuators and having a split collar portion bearing uponthe shaft, said arm tending to be rotated with said collar in thedirection of rotation of the shaft and to push one of the 10 actuatorsto tend to open the movable contact engaged thereby, the eccentrictending to close periodically a relatively fixed contact with a movablecontact held open if said shaft comes to rest during continued operationof the motor, thereby de-energizing the motor.

References Cited by the Examiner UNITED STATES PATENTS 761,876 7/1904Clark 200-105 1,996,849 4/1935 Bauer 192-150 2,484,616 10/1949 Dulaney318-475 X 2,954,224 9/1960 Schneider et a1. ZOO-61.46 X

BERNARD A. GILHEANY, Primary Examiner. T. MAcBLAIN, R. N. -ENVALL,Assistant Examiners.

2. THE COMBINATION OF A MOTOR, A DRIVEN SHAFT, A ROTOR HAVING MEANS FORDRIVING IT FROM THE MOTOR AND HAVING SLIP CLUTCH CONNECTION WITH THESHAFT FOR NORMALLY OPERATING THE SHAFT FROM THE MOTOR, AN ECCENTRICCONNECTED WITH THE ROTOR, A YOKE RIDING ON THE ECCENTRIC TO RECEIVEMOTION THEREFROM, A SWITCH MOUNTED ON THE YOKE AND HAVING NORMALLYCLOSED CONTACTS, A MOTOR CONTROLLING CIRCUIT IN WHICH SAID SWITCH ISCONNECTED, AN ARM HAVING FRICTION DRIVE CONNECTION WITH THE SHAFT TORECEIVE MOTION THEREFROM TENDING TO ROTATE THE ARM WITH THE SHAFT, MEANSFOR OPENING ONE OF THE CONTACTS OF THE SWITCH WITH RESPECT TO THE OTHEROF SAID NORMALLY CLOSED CONTACTS AND CONSTITUTING AN ACTUATOR COMPRISINGMEANS FOR RECEIVING MOTION FROM SAID ARM WHEN SUCH MOTION IS IMPARTEDFRICTIONALLY TO THE ARM FROM SAID SHAFT, WHEREBY THE SWITCH TENDS TO BEHELD OPEN DURING SHAFT ROTATION, SAID ECCENTRIC AND YOKE CONSTITUTINGMEANS EFFECTIVE DURING CONTINUED OPERATION OF THE ECCENTRIC FOR BRINGINGABOUT THE CLOSING OF THE SAID SWITCH CONTACTS OF SAID SWITCH WHEN SHAFTMOTION IS ARRESTED.